Twin-screw armored cable connector



May 2, 1950 M. D. BERGAN 2,506,334

TWIN-SCREW ARMORED CABLE CONNECTOR Filed June 2. 1947 INVENTOR.

WA /970v Q patented May 2, 1950 UNITED TWIN-SCREW ARMORED CABLECONNECTOR Martin D. Bergamwestfield, N. J assignor to The Thomas & Betts00., Elizabeth, N. J., a corporation of New Jersey Application June 2,1947, Serial No. 751,716 3Claims. (Cl. 285-65) The invention relates toelectric connectors of the type designed to secure conductors such as BXcables to an outlet box.

It is known at, present to provide a tubular form of outlet boxconnector which is secured to an opening in the outlet box invariousways,

and in which a cable is intruded into a tubular portion and arranged topermit a cut back portion of the cable to engage a, bushing or stopflange on the inner end of the tube and which tubular portion isprovided in the accessible part oi the connector exteriorly of theboxwith different forms of clamping devices for securing the cablethereto. I I

In general, the connectors of this type now on the market are designedto accommodate only a few'sizesof conductors or cable with a limitedrange of maximum to minimum diameters.

There has recently appeared on the market a new type of BX cable ofrelatively'small diam eter. It is physically impossible'to use thepresent forms of connector to secure both the usual size and the newsmall diametered conductor to the box. 7 v

The primary object of the invention is to provide a standard form ofconnector which'can be used to receive and secure to the outletbox anydiameter of cable within the scope of those which can be intruded intothe bore of the tubular part of the connector including the larger typesmarketed for many years plus the small size recently added to themarket.

' Broadly this objective is obtained by utilizing two screws intransversely offset relation and operatively disposed to engage andsecure in place in the connector conductors or cables of any diameterwithin the capacity of the tube. bore. It has been known heretofore touse a single screw, sometimes called a tangential screw, arranged toengage the intruded conductor or cable oil'set from the axis of the samein order to avoid crushing the usual metal shell on BX conductors aswould happen if the screw engaged the'shell or armor in line with itsaxis. The present disclosure contemplates the retention of thistangential engagement of the conductors or cables irrespective of theirdiameters. It has been suggested in the case of the single screwclamping arrangement to provide a screw of sufficiently large diameterto contact the small size contained cable irrespective of its diameter..

It has been found, however, that this suggested arrangement is tooexpensive and the dual screw assembly herein featured is found to becheaper to manufacture than any such abnormally size screws. The presentinvention features in the case of the small diametered cable, the use orone of the screws not as a clamping device, but as a shifting orlocating device for laterally shifting the small diametered cable intoposition to be engaged by the other screw functioning as a clamp andpreferably to have the other screw engage the cable in the preferredform of. off centered contact. r Various other objects and advantages ofthe invention will bevin part obvious from an inspec tion of theaccompanying, drawings and in part will be more fully set forth in thefollowingparticular description of two forms of dual screw clampembodying the invention, and the inven; tion also consists in certainnew and novel fe'atures of construction and combination of partshereinafter set forth and claimed. In the accompanying drawings: Figure1 is a view in axially, vertical section of a connector constituting apreferred embodiment of the invention operatively securing a conductorof relatively small diameter to an outlet box; and taken on the brokenline l-l of Fig. 4; t

Figure 2-is an end view of the showing of Figure l as viewed with arelatively large diametered cable substituted for the smallercabletherein shown, and with one of the screws removed from theconnector, and in general showing a known structure; I

Figures 3 and 4 are views in end elevation taken on theplane indicatedby the line 4--4 of Figure 1 looking in the direction of the arrow andshowing the small diametered cable in transverse'cross section; Figure 3showing the first step in the manner herein featured of shifting theconductor cable laterally before it is locked in the connector; andFigure 4 showing'the parts in their final locked position and whichlocked position is also shown in Figure 1;

' Figure 5 is anotherview corresponding insofar as the connector is'shown to Figures 3 and "4; showing both screws advanced into a dualclamping engagement with a cable of intermediate size;

Figure 6 is a horizontal'sectional view taken on the line 6'-'-6 ofFigure 1, looking downwardly and showing the two screws in dottedoutline with their intruded ends engaged in a trough be tween twoadjacent turns of the spiral corruga'j-L tion of the cable and;

. Figure .7 is a view in vertical longitudinalsec; tion of the connectorshown inthe preceding figures taken axially through either I screw andwith slightly modified form of screw substituted trusion of any sizecable generally designated as C into the tubular member. The member IIis provided in spaced relation to both of its ends with an outstandingcorrugation I'd which forms abutment for engaging against the outer sideof the box and thus acting as an. abutment toliniit the intrusion of theconnector into the box. The portion of the connector which is intrudedinto the hole B forms an extension I exteriorly threaded as at [Handwhich isengaged by a not H'to clamp the wall of the sex between the cor=rugation I4 and not H. The outwarmy extend" his portion 18 or theconnector a cross-=sse= tional configuration, as shown in Figures 2 to5, ifvhlth includes a curved substantially semi=cylin= drical bottomside or seat l9 and a relatively flat up er side '20. The seat 19 andthe flat top side are integrally connected at opposite sides by u'p'=standing parallel sides 2 r 22, to coact therewith to form a ring-likeband I'-he structure as thus for described is somewhat ii -conventionaldesign. The particular feature of this disclosure is that too ordinarymachi e screws and 2 4 are threaded through the not upper side 20 intrans- ?eisely spaced apart parallel relation, designed in the case orthe larger size conductor as shown in Figure 2 to ave either screwengage a large size conductor on either sideof its axis D. Irlthe casewhere the larger site conductor is used, either screw, such for instanceas the left screw 13; may be entirely omitted and finder thesecirel'i'ihstances the device resembles known structure except of course,for the presence or the screw hole for receiving the screw 23.

Assuming a small -Bi-ze'co'r'iduc'toi or cable SC is inserted into thetubular member as indicated assures L, -3 and 4-, the right screw 24 isadvanced erereraoiy to the lit-nit of its movement shown in Figure 3engaging the cable SC tangently and withits intruded end engaging or"almost engaglhg the (curved side or seat 1 9. In this case the rightscrew 24 extends into the bore l-2 for a dis tonne more than one-halfthat between the flat side 253 and the curved bottom side !9. Thishasthe effect of pushing the conductor SG laterally towards the left sothat the conductor SC is squeezed between the side of the screw 24 andthe left side of the curved seat portion. and substantially in the lineof thrust of the left or binding screw 23. With a small diametere'dconductor so located in place and fixed against shifting transversely,theleft screw is advanced inwardly and thus ;into binding engagementwith the conductor SC as shown in Figure 4. It is thus seen that theright screw is-not functioning in this case as a binding screw but as ameans i or reducing the horizontally cross section of the bore l2. Whilethese two extreme positions have been indicated and illustrated resectively in figures 2 and 4,

4 be advanced more or less equally and thus used as dual clampingscrews.

In the showing in Figures 5 the screws 25 and 26 are of equal length,more nearly of the size of the shorter screw 23 and engage theintermediate size cable on opposite sides of it crown and thus to locatetheir lines of thrust oifset from the axis of the cable IC. In thiscase, the underside of the cable IC fits more or less snugly on the seatl9 and substantially centered in the connector.

In this way, the two screws 25 and 25 can be ad- Vvanced equally todistribute pressure more or less equally on the intermediate size cablesor even on the large size cable LC of Fig. 2, or one screw can beadvanced beyond the other if such permissible unrelenting or pressurebecomes feasible for any reason.

Thearrangement of the screws as thus far desciibd'consider their axes aslocated more or less accurately in the same transverse plane. Assugees-ted in Figure- 6; the screws may be relatively ofi set slightlyaxiany of the bore or otherwise so spaced that their intruded ends willbear in the troughs E formed between the corrugations F of the cablearmor G. a

In the preceding figures; the screws have been shown to be of the usualtype of fiat ended ma chine screws. Of course, such screws are extremelycheap and this is a controlling reason for their use. It'is suggested;however as shown in Figure '7 that the intruded ends of the screws 21 betapered to show fingers 28 0f frusto-conica1 de sign and dimensioned tofitbetween adiacentsides H and I of the corrugations F as they turn orround inwardly from their-crown -J to form the troughs E. This structurehas the additional advantage of forcing the conductor or cable 0irrespective of its or their diameters from right to left of the showingin Figure 1 as indicated by the rrow in Figure 7 soas to force its endbushing K into firm engagement with its stop or bushing flange I3.

In this way the connector Ii) may be supplied as a standard size unitand simply by substituting' the necessary size and type 'of screw, whichthe operator can. carry with him in stock, the connector may beconveniently set up to receive the particular size or cable indicatedfor. the ill-'- stant job.

1. A sheet metal connector for securing a cable to a box having anopening in a side thereof, said connector including a tubular memberwith one end threaded and to extension for insertlon into't'he box"opening, said tubular member rovideo exterioriy 'witha cor ugationadjae o'ent its midl'ength to forms. stop iorengaging one side oithe boxand to limit the intrusion-or connector into the box, said memberprovided at its inner end with inwardly bent ortion for-mini; a pushingfor limiting the intrusion of the cable into the member, the other endof "the tubular member when considered in cross "section having a fiattop side, a curved bdbti3miae forming' a seat for the cableandfpa'Xall-l side walls connecting the "bottom "and sides and a pair ofscrews spaced apart transversely of the axis or the here on oppositesides thereof spaced apart axially and threaded through the hat to sideclosely adjacent the corrugation-for engaging the conductor for the timebeing in the bore of the tubular part, at least one o'i s'a-id screwshaving a length to extenonrore than half Way from-the flatto the curvedsid-eto iili up approximately the spacein "one-half *of thdboleldssection laT/ 5 ing the balance of the-bore cross section open to receivea cable therein positioned to be engaged by the other screw.

2. In a device of the class described, the combination of a tubularmetallic connector provided with a bore for receiving cables ofdifferent diameters, a cable within the bore having materially lesscross section than the cross section of the bore, thus leaving a spacein the bore not occupied by the cable, a pair of screws threaded throughthe side of the connector and disposed in relative transverse relation,the portions of the screws within the bore forming fillers tending tooccupy the space considered transversely not occupied by the cable andat least one of the screws having its free end within the bore bearingon the cable and acting along a thrust line offset from the axis of thecablethereby to clamp it at three points, that is, at the advance end ofsaid screw, at the portion of the connector opposite the screw, and atthe other screw.

3. A connector including a tubular part pro- REFERENCES CITED Thefollowing references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 649,744 Neal May 15, 19001,606,814 Seidel Nov. 16, 1926 1,677,628 Gould July 1'7, 1928

